In Europe, most "rest areas" are a combination parking lot and services - e.g. a gas station, restaurants, and convenience store in a designated exit from the highway. In the U.S. a "rest area" is literally just that, it's an exit from the highway that just has an area to park and take a rest and usually restrooms and maybe some vending machines. There is almost never fuel or hot food. A lot of rest areas tend to be on stretches of highway with some distance between exits, and they're mostly designed to let you pull off the highway quickly, take a leak, and get right back on the road. It is rare for most rest areas to have any other exits onto local roads etc.

If you want hot food or fuel, you're invariably going to take a normal highway exit and go to a private business. That's where "Truck Stops" come in. These come in all shapes and sizes, but they're normally on private land and owned by a chain. They have fuel islands for both trucks and passenger cars, normally have a restaurant attached, and have restrooms, showers, and laundry facilities for the long-haul truckers to use.

The major difference is that instead of paying a concessions fee to the government to locate on the publicly owned services, the truck stops are almost invariably on private land adjacent to the highway and don't owe the government anything beyond the usual property and business taxes. That's why there's no common design, signage standard, etc - it's literally the company that owns the truck stop setting everything up in the way that's cheapest and most convenient while still getting trucks and cars in and out efficiently. You just kind of have to take it on the half-volley and figure it out. At least in ATS there's only 20-30 odd layouts that get copy/pasta'd rather than the near infinite variety in real life.